1. Field of the Invention
The present invention generally relates to a power supplying mode switching controller, an image forming apparatus using the power supplying mode switching controller, and an image reading apparatus using the power supplying mode switching controller.
2. Description of the Related Art
In an image processing apparatus such as a printer, a scanner, and a copier in which low cost operations by low power consumption are realized, at least two power supplying modes of a normal mode and a power saving mode are provided. In the normal mode, the apparatus can perform functions, for example, printing by supplying power to all the functions. In the power saving mode, power is only supplied to circuits for detecting user operations of the apparatus and detecting access from an external device and for storing information necessary to be maintained; the power is cut off to a circuit which executes printing (scanning) when the printing (scanning) is not being executed. A controller in the apparatus generally provides a main CPU and a sub CPU. The main CPU controls printing (scanning) operations and enters a power cutoff mode (sleep mode) in the power saving mode when printing is not being executed. The sub CPU enters an idle mode (sleep mode) in the normal mode, and detects a signal to return to the normal mode in the power saving mode.
In Patent Document 1, a network controller is disclosed. In the network controller, in order to realize low power consumption, in addition to a CPU, a sub CPU is provided. When the normal mode is switched to the power saving mode, the sub CPU processes packets in a network and prevents packet loss (communication loss).
[Patent Document 1] Japanese Laid-Open Patent Application No. 2005-303978
When the sub CPU detects a factor for returning to the normal mode from the power saving mode of the apparatus, the sub CPU switches from the power saving mode to the normal mode. However, in order that the sub CPU detects the factor to return to the normal mode in the power saving mode, the sub CPU must provide a device driver for an I/F to which the factor for returning to the normal mode is applied on software (operating program) in the sub CPU, which device driver is similar to that in the main CPU. Consequently, a time period and labor hours for developing software for the sub CPU are required, and a program storing area in the sub CPU is increased. With this, the cost is increased and the power consumption is increased.
For example, the apparatus controls a detachable recording medium by software (operating program) on the main CPU. In the apparatus, the software operating on the main CPU must recognize information to determine whether the detachable recording medium is changed or a new recording medium is attached to the apparatus in the power saving mode (low power consumption mode). However, in the power saving mode, in order to realize the low power consumption mode, since the main CPU is in the idle mode (sleep mode), or in a power cutoff mode, the main CPU cannot determined whether the detachable recording medium is attached/detached to/from the I/F. For example, in a case where the normal mode is switched to the power saving mode while the detachable recording medium is being loaded, when the detachable recording medium is detached and a new detachable recording medium is attached in the power saving mode, the software on the main CPU must recognize that the detachable recording medium is changed.
In addition, the apparatus controls a communication I/F which can make a host computer wait (for example, a PC (personal computer)) to operate. In the apparatus, the software operating on the main CPU must recognize whether a host computer is attached to the communication I/F or detached from the apparatus. However, in the power saving mode, in order to realize the low power consumption mode, since the main CPU is in the idle mode, or in the power cutoff mode, the main CPU cannot determined whether the host computer is attached to the communication I/F or detached from the communication I/F. For example, in a case where the normal mode is switched to the power saving mode while the host computer is being attached to the communication I/F, when the host computer is detached from the communication I/F and a new host computer is attached to the communication I/F, the software on the main CPU must recognize that the host computer being attached to the communication I/F is changed.
In order to inform the software on the main CPU of information whether the detachable recording medium is changed or the host computer is changed in the power saving mode, it is possible that the software on the sub CPU detects that the detachable recording medium is detached and a new detachable recording medium is attached and inspects data in the detachable recording medium, or the software on the sub CPU detects that the host computer is detached and is attached again and executes data communication with the host computer attached to the communication I/F. In this case, a device driver is required on the sub CPU which device driver can read/write data from/on the detachable recording medium on the software of the sub CPU or can execute data communication with the host computer attached to the communication I/F. However, when low power consumption is required, the ROM capacity must be a necessary minimum to store software. In addition, in order to achieve low power consumption, since a CPU having low throughput and low operating frequency is used as the sub CPU, time to determine whether the detachable recording medium is changed or to execute data communication with the host computer attached to the communication I/F becomes long.
In addition, after the software on the sub CPU returns the main CPU to the normal mode by determining that the detachable recording medium is changed or the host computer attached to the communication I/F is changed, the software on the main CPU must execute a mounting process and an unmounting process of the above information on a memory corresponding to the change.